1. Field of the Invention
The present invention relates to an electronic camera that captures a subject image and records image data.
2. Description of the Related Art
There are electronic cameras in the known art having an image-capturing device and an image processing circuit. The image capturing device captures a subject image having passed through a photographic lens with a CCD or the like and outputs image data. The image processing circuit implements image processing such as white balance adjustment and γ control by adjusting the amplification gain to be applied to the image data output by the image-capturing device. In the image processing circuit, the image processing is performed by calculating parameters such as the R-gain and the B-gain for the white balance adjustment, the gradation curve for the γ control or the like using predetermined algorithms based upon the image data output from the image-capturing device.
The white balance adjustment may be performed in an electronic camera by adopting one of the following three methods in the known art, for instance. The first method is disclosed in Japanese Laid-Open Patent Publication No. S56-36292. A white balance adjustment coefficient is calculated so that the average value of color information corresponding to the main subject, the background and the like obtained through an image-capturing operation becomes an achromatic color that may be white or gray. Then, a white balance adjustment is implemented on the image data by using the adjustment coefficient thus calculated.
The second method is disclosed in Japanese Laid-Open Patent Publication No. H 5-292533. An image plane to be photographed is divided into a plurality of small areas and a small area whose average value of the color information is within a predetermined range is extracted. Then, a white balance adjustment coefficient is calculated so that the average value of the color information corresponding to the extracted small area to indicate an achromatic color and a white balance adjustment is implemented on the image data using the adjustment coefficient thus calculated.
The third method is disclosed in Japanese Laid-Open Patent Publication No. 2000-224608. A small area indicating a specific color is extracted from the photographic image plane, a white balance adjustment coefficient is calculated so as to set the color in the extracted small area to a specific color and a white balance adjustment is performed on the image data using the adjustment coefficient thus calculated.
While each of the white balance adjustment methods described above has its advantages, they all have problems to be addressed. Accordingly, Japanese Laid-Open Patent Publication No. H 6-98335 discloses a technology through which one of the three white balance adjustment signal calculation methods is selected. However, there is a concern that as the white balance adjustment value may change greatly over an area where a borderline of judgment performed to select one of the methods is present, the image having undergone the white balance adjustment may appear unnatural in such a case. In addition, an image with unnatural color results from an error in the selection judgment process and thus, a white balance adjustment failure occurs readily.